The assignment of an internet protocol (IP) address to a device by means of DHCP (Dynamic Host Configuration Protocol) is known from the prior art. DHCP is normally used in Local Area Network (LAN) environments for allocating IP addresses from a central address server.
The selection of the IP address that must be assigned to the requesting device is performed by the DHCP server using the local settings (static or dynamic allocation) and the options that are supplied in the DHCP request. The DHCP server can unambiguously assign the locally stored IP address to a client by means of the DHCP options (cf. internet page http://www.iana.org/assignments/bootp-dhcp-parameters) “#12 Host Name Option”, “#43 Vendor Specific Option”, “#61 Client Identifier”, “#82 Relay Agent Information”, “#128-254 Private Use” or a further option that is newly defined.
In order to allow this unambiguous assignment, the selected identifier (identification code) must be unambiguous in all variants throughout a LAN.
This identifier must be residually stored on the client, so that a replicable result for the address resolution can be obtained. A UUID (Universal Unique Identifier) or a DNS (Domain Name Service) name, for example, can be used as an identifier for a client or a port of a client. A plurality of identifiers (aliases) for an IP address can be stored in the DHCP server.
As a result of the “#82 Relay Agent Information” in the DHCP, the terminal that requests the IP address can be accurately identified by the port of the coupling node (switch) to which it is connected. The option 82 is comparable with an identification via Media Access Control (MAC) address. It has the advantage that the identification takes place at Level 3 of the Open System Interconnection (OSI) layered model, and is therefore supported by the IP protocol (concerning this, see also IEE 48. Year 2003 No. 11, Pages 32 to 34, “Netzmanagement für Ethernet, Schritt in die richtige Richtung” [Network management for Ethernet, a step in the right direction], Frank Seufert).
The assignment of IP addresses by means of DHCP and “#82 Relay Agent Information” is also disclosed in the US patent applications US-A-20040010653 and US-A-20030101243.
A disadvantage of the assignment of IP addresses by means of DHCP and Option 82 is that the switches are heavily loaded by the resource-intensive filtering of the DHCP requests. A switch must identify all DHCP requests by means of such a filter and remove them from the data stream for the purpose of entering additional information or recognizing that an entry already exists. The DHCP request is then reinserted into the data stream. It is particularly disadvantageous here that efficient switching mechanisms such as cut-through are rendered impossible.